the Animals of the Deep Seas. 



197 



6 centlras. high ; that of the larger one (fig. 2) 53 centims. 

 long, 28 centims. broad, and 16 centims. high. The two 

 larger perpendicular walls were glass plates*. 



Fiff. 1. 



Surface of Water 





^^^^^^m,^^~^~'-i. .< 



The bottom of the smaller aquarium, after it had been filled 

 with water, was covered with a thin layer of sand, to which I 

 gave an inclination of about 5° (fig. 1). I then, by means of 

 a spoon, allowed fine mud-particles, which had been sifted out 

 of the mud of the mud-region of the harbour of Kiel, to sink 

 slowly down upon one of the narrower sides of the aquarium, 

 until a slope of 35-40° had been formed. The heaped-up 

 mass was inhabited by a number of small animals. Gammarus 

 locusta, Cuma Rathkit, Joira aibifronSj ScoIojjIos armigevy 

 Nemertes gesserenst's, Monocelis agtlts, Pontolwiax capitatus^ 

 Corhula gihha^ Tellina halthica^ and Scrohicularia alba soon 

 made themselves visible in the superficial layer. The next 

 day the mass had settled a little, and its lower boundary had 

 already perceptibly advanced. On the third day its progress 

 was already 3 centims. I now laid a few spoonfuls of sand 

 upon the uppermost part of the slope, and then disturbed the 

 equilibrium of the water for a few minutes by moving a finger 

 up and down in it. By this means the abruptly rising sand 

 acquired a more oblique direction, and covered the mass of 

 mud for a breadth of several centimetres. Two days later, 

 this sand had for the most part sunk down into the mass of 

 mud and pushed it still further forward even at the bottom. 

 Its angle of inclination had decreased from 35-40° (its original 

 amount) to 25°, and the sand spread over the horizontal bot- 

 tom was covered throughout with fine mud-particles (fig. 1, 

 line a, b, c). 



* The two figures represent profiles of tliese aquaria. The dotted line 

 indicates the future surface of the organic mass. In fig. 2 the arrows 

 indicate the direction of the sinking current. 



